The present invention relates to an image display method and an image display system in case of designing a three-dimensional configuration and the like.
When a three-dimensional configuration is displayed with a CAD system and so on, an operator judges the quality of the configuration, watching the three-dimensional configuration from an optional direction and performs a combining operation of various configurations. This is for forecasting and judging workmanship of an object to be designed or to design objects only by data processing with a computer without actually producing the object, and for producing configuration information of the object to be designed. Further, in order to forecast in advance, when an operation command is given to a machine tool, a robot and the like, how they are operated and to what extent they interfere with other members, it is required to observe raw materials, tools, parts, arms and the like on a computer image plane.
When it has been desired to display a three-dimensional image on an image screen from a certain other point of view, for example, when a certain object being displayed is desired to be viewed from the right side or from the left side, the viewing direction has been heretofore designated as follows.
For example, in a most fundamental first prior art, the direction is designated by numeric values. That is, a directional vector line of sight and a vector in an upward direction on an image screen are designated with numeric values and an angle of rotation from a reference direction is designated with numeric values in an ordinate system in a three-dimensional space.
In a second prior art, the viewing direction is selected by having numerals correspond to several display directions which have been prepared in advance (for example, "1" corresponds to the direction viewed from the front, "2" corresponds to the direction viewed from the right and so on), and designating the corresponding numeral to a particular direction. That which is related to this second prior art is described in a manual "HITAC Program Product GRADAS Three-Dimensional Design System HICAD/3D Principles of Operations (8090-7-034-40) p. 155 issued by Hitachi, Ltd.
In a third prior art, when a certain three-dimensional image has already been displayed, rotating angles for further rotating the three-dimensional image which is being displayed (angles viewed from top and bottom, angles viewed from right and left, angles for rotating clockwise and counterclockwise around an axis which is perpendicular to the image screen and so on) are input from a dial or a keyboard by designating numeric values. This prior art is also described in page 150 of the manual of the second prior art.
In a fourth prior art, one straight line in a displayed configuration is designated as an axis of rotation, and the image is rotated around the axis by a rotating angle designated by one dial.
In a fifth prior art, a display direction of a configuration which is newly displayed is designated using several points, lines or faces in a configuration which is being displayed. For example, when two straight lines which are perpendicular to each other are designated, the configuration is displayed so that the straight line designated at the beginning becomes the horizontal direction of the configuration which is newly displayed and the straight line designated later becomes the vertical direction. (This prior art is described on page 154 in above-mentioned manual, and will be described later with reference to FIG. 17.) Further, when one face and one straight line which is parallel to the face are designated, the configuration is displayed so that the designated face is parallel to the display screen and the designated straight line shows a horizontal direction.
In a sixth prior art, when one sphere is displayed and one point on the sphere is designated, a body is displayed with a vector connecting the point and the center of the sphere to determine direction.
As other prior arts reference, JP-A-1-305475 and JP-A-61-46565 may be mentioned as being relevant.
According to the prior arts described above, it is possible to display a three-dimensional image when a design object is viewed from an optional direction. For example, in the above-described fifth prior art, an operator designates a straight line 201 on a right side surface and a straight line 202 on a bottom surface one after another as seen on the design object shown in FIG. 17A which are seen from various directions and are displayed on the image screen. Accordingly, the design object is displayed so that the straight line 201 lies in a horizontal direction and the straight line 202 lies in a vertical direction on the left side of the image screen as shown in FIG. 17B. Also, when the operator designates the straight line 202 and the straight line 201 in successive order, the display is made so that the straight line 202 lies in a horizontal direction and the straight line 201 lies in a vertical direction as shown in FIG. 17C. Furthermore, when the operator designates a straight line 202 and a straight line 203, display is made so that the straight line 202 lies in a horizontal direction as shown in FIG. 17D.
It is possible for an operator to designate the display direction of a design object optionally as described above, but questions arise regarding accuracy and ease of the designating operation. In respective prior arts described above, no consideration has been given to ease of the designating operation, thus the operation remains complex and inconvenient. For example, when it is desired to look at the image shown in FIG. 17C, the operator has to determine which two straight lines are to be designated in FIG. 17A and how the designating order should be, by picturing in the operator's brain, the displayed image in FIG. 17C in a three-dimensional coordinate system to oneself in advance. With such a method, the operator has to repeat trials and errors until an objective image is obtained. The same applies to other prior arts, and furthermore, only an image in a predetermined direction can be seen and a display direction has to be designated with numeric values, thus requiring operating sense which is different from design intentions of the designer.